More than forty lysosomal storage diseases (LSDs) are caused, directly or indirectly, by the absence of one or more lysosomal enzymes in the lysosome. Enzyme replacement therapy for LSDs is being actively pursued. Therapy generally requires that LSD proteins be taken up and delivered to the lysosomes of a variety of cell types. The inventors of the present application have previously developed a peptide-based targeting technology that allows more efficient delivery of therapeutic enzymes to the lysosomes. This proprietary technology is termed Glycosylation Independent Lysosomal Targeting (GILT). Details of the GILT technology are described in U.S. Pat. Nos. 7,396,811, 7,560,424, and 7,629,309; U.S. Application Publication Nos. 2003-0082176, 2004-0006008, 2003-0072761, 2005-0281805, 2005-0244400, and international publications WO 03/032913, WO 03/032727, WO 02/087510, WO 03/102583, WO 2005/078077, the disclosures of all of which are hereby incorporated by reference.
Because proteins utilized in enzyme replacement therapy are larger and more complex than traditional organic and inorganic drugs (i.e., possessing multiple functional groups in addition to complex three-dimensional structures), the formulation, packaging and preservation of such proteins poses special problems.